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#2553120 - 09/21/18 10:11 PM Radiator cap
cdstl Offline
super stock

Registered: 09/03/11
Posts: 1099
Loc: STL
My son's Duster with a 408 and a Champion radiator.

The car cools fine. The thing is this, with the Champion cap on, the hoses swell up like a tick that's about to explode. I put a JY 16 pound cap on and it's a little better but still the hoses are very, very rigid and expanded.

I saw an Allpar article on Radiator caps. I guess they cover everything.

Here is what they say about the valve that is at the bottom of the cap....

1976 FSM (Factory Service Manual) has to say on page 7-8:

The vent valve at the bottom of the cap should hang freely. If the rubber gasket has swollen and prevents the valve from hanging loosely, replace the cap. Hold cap in hand upside down. If any light can be seen between vent valve and rubber gasket replace cap. Do not use a replacement cap without this vent valve that hangs freely.

Ok, so I took the cap out of my Cuda and the valve hangs freely and I put it on his Duster and guess what. The temp stays where it should and the hoses are not ready to burst.

The question is who carries the cap that he needs?

Thanks
_________________________
1972 Cuda 340 auto, 2001 Ram CTD 4x4 6 speed, 1970 Duster 408 4 speed, 2001 Ram 5.2 4x4 auto, 1996 Ram 5.9 2x4 auto

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#2553177 - 09/22/18 07:36 AM Re: Radiator cap [Re: cdstl]
cdstl Offline
super stock

Registered: 09/03/11
Posts: 1099
Loc: STL
Ok so from what I have learned I have a recovery cap on my Cuda and I would like to get another for the Duster. Before I go and order a cap and find out it's not the recovery type, do you guys have any suggestions as to who would have the correct cap?

Thanks
_________________________
1972 Cuda 340 auto, 2001 Ram CTD 4x4 6 speed, 1970 Duster 408 4 speed, 2001 Ram 5.2 4x4 auto, 1996 Ram 5.9 2x4 auto

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#2553180 - 09/22/18 08:15 AM Re: Radiator cap [Re: cdstl]
Supercuda Offline
I Live Here

Registered: 09/04/07
Posts: 13835
Loc: up yours
Originally Posted By Frank Raso
See Allpar: Cooling systems: the surprisingly wide range of radiator caps.

16 psi partial pressure rad caps are available from Chrysler, PN 52079880AA.

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They say there are no such thing as a stupid question.
They say there is always the exception that proves the rule.
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#2553192 - 09/22/18 09:11 AM Re: Radiator cap [Re: cdstl]
cdstl Offline
super stock

Registered: 09/03/11
Posts: 1099
Loc: STL
Well heck. I just checked the "Cuda" cap vs. the cap on my 1996 Ram. Same cap. I guess the Cuda cap WAS the JY cap.

Now just to go shopping at the Junk Yard.

Thanks
_________________________
1972 Cuda 340 auto, 2001 Ram CTD 4x4 6 speed, 1970 Duster 408 4 speed, 2001 Ram 5.2 4x4 auto, 1996 Ram 5.9 2x4 auto

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#2553499 - 09/23/18 02:10 AM Re: Radiator cap [Re: cdstl]
383man Offline
Too Many Posts

Registered: 01/19/03
Posts: 26879
Loc: Balt. Md
There is no special cap for the recovery system. All rad caps will release at the set pressure and all have the vacum release also. Its just that when it has the recovery tank the coolant released at the pressure setting will go into the tank instead of on the ground. And then when the vacum release valve opens with the recovery it pulls the coolant back into the rad which the older cars without the recovery tank cant do that since the coolant went on the ground. But the caps all worked the same other then different pressure settings which for every lb of pressure on the coolant raises the boiling point 3 degrees. Ron


Edited by 383man (09/23/18 02:11 AM)
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My car...63 Sport Fury Max Wedge wanna be street car..with new 493 pump gas full exh eng.......10.76 @ 124.49 ! ! ! My page on the cool 62-65 Mopar site ! http://www.1962to1965mopar.ornocar.com/mmo82008.html

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#2553512 - 09/23/18 04:34 AM Re: Radiator cap [Re: cdstl]
tman Offline
mopar

Registered: 08/21/07
Posts: 442
Loc: WA
You can get a replacement from any parts store. You are looking for a Vented or Closed system. This is a quick explanation of the differences:

https://jimdinner.wordpress.com/2012/07/09/radiator-caps-explained/

I recently turned my open system to closed by adding a recovery tank, so I had to get a new cap from Oreilly's. This would work, unless you are looking for stock look. Similar as the Mopar cap

https://www.amazon.com/Stant-10231-Radiator-Cap-Vented/dp/B000B8N3GE/ref=au_as_r?_encoding=UTF8&Make=Plymouth%7C43&Model=Barracuda%7C2302&Year=1970%7C1970&ie=UTF8&n=15684181&s=automotive&vehicleId=3&vehicleType=automotive

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#2553521 - 09/23/18 07:07 AM Re: Radiator cap [Re: 383man]
cdstl Offline
super stock

Registered: 09/03/11
Posts: 1099
Loc: STL
Originally Posted By 383man
There is no special cap for the recovery system. All rad caps will release at the set pressure and all have the vacum release also. Its just that when it has the recovery tank the coolant released at the pressure setting will go into the tank instead of on the ground. And then when the vacum release valve opens with the recovery it pulls the coolant back into the rad which the older cars without the recovery tank cant do that since the coolant went on the ground. But the caps all worked the same other then different pressure settings which for every lb of pressure on the coolant raises the boiling point 3 degrees. Ron


At the yard yesterday I found 2 caps with the vent valve that hung freely. Just like in the Allpar quote that I have above. They came off of some Dodge Rams. I also found a couple of caps that had the vent valve that did not hang freely off of another Dodge Ram. And of course, they were all recovery systems.

I've got one of them on the Duster now and I'll have a spare.
_________________________
1972 Cuda 340 auto, 2001 Ram CTD 4x4 6 speed, 1970 Duster 408 4 speed, 2001 Ram 5.2 4x4 auto, 1996 Ram 5.9 2x4 auto

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#2553549 - 09/23/18 09:00 AM Re: Radiator cap [Re: 383man]
pushbutton Offline
pro stock

Registered: 11/15/08
Posts: 1424
Loc: tennessee
[quote=383man]There is no special cap for the recovery system.

I disagree,they will all push coolant out,but they all won't suck it back,unless there is another style cap out there that I'm not aware of.
PB

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#2553651 - 09/23/18 12:47 PM Re: Radiator cap [Re: cdstl]
RapidRobert Offline
Circle Track

Registered: 11/20/03
Posts: 34151
Loc: Lincoln Nebraska
Quote:
The thing is this, with the Champion cap on, the hoses swell up like a tick that's about to explode.
any possibility that you have a combustion leak into the coolant system? EDIT that takes alot of psi to expand em out like that, You could get a "tank valve" from Oreillys for less than $3 & screw it into the cooling temp sensor port & pump it up to say 10 psi & see if it hold pressure (check with your tire gauge). This ain't the same as major compression psi coming from the other direction into the cooling system but it would be a start (& cheap/easy). with the eng full of coolant/not much dead air space it will reach 10 in a heartbeat so put the air chuck from your shop air on there for a split second at a time (it ain't like airing up a tire that takes minutes). The last thing you wanna do is blow up your hoses!


Attachments
SAM_0837.JPG




Edited by RapidRobert (09/23/18 12:56 PM)
Edit Reason: bored
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#2554146 - 09/24/18 03:07 PM Re: Radiator cap [Re: pushbutton]
383man Offline
Too Many Posts

Registered: 01/19/03
Posts: 26879
Loc: Balt. Md
Originally Posted By pushbutton
[quote=383man]There is no special cap for the recovery system.

I disagree,they will all push coolant out,but they all won't suck it back,unless there is another style cap out there that I'm not aware of.
PB



Actually you could be right. I will say all the caps I have used have the pressure and vacuum release and years ago in auto shop they never said the old caps did not have the vacuum release also. But maybe the caps I have used have been sine they went to the recovery system which was in the 70's I believe. And you are right that the old system did not need the vacuum release since they had no recovery tank to pull the coolant back in. I have never ben told they were different so I assumed they were not but I could be wrong on that and if I am I appoligize. Ron
_________________________
My car...63 Sport Fury Max Wedge wanna be street car..with new 493 pump gas full exh eng.......10.76 @ 124.49 ! ! ! My page on the cool 62-65 Mopar site ! http://www.1962to1965mopar.ornocar.com/mmo82008.html

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#2554155 - 09/24/18 03:32 PM Re: Radiator cap [Re: 383man]
John_Kunkel Offline
I Live Here

Registered: 01/20/03
Posts: 19683
Loc: Rio Linda, CA
The main component of a coolant recovery cap that allows recovery is the rubber top gasket that seals against the filler neck, without it the vent simply pulls air into the system when a vacuum is present in the system.

Non-recovery caps usually have a metal disc in place of the rubber top gasket.
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#2554327 - 09/24/18 11:28 PM Re: Radiator cap [Re: John_Kunkel]
rhad Offline
super stock

Registered: 08/19/03
Posts: 709
Loc: garnett kansas
Originally Posted By John_Kunkel
The main component of a coolant recovery cap that allows recovery is the rubber top gasket that seals against the filler neck, without it the vent simply pulls air into the system when a vacuum is present in the system.

Non-recovery caps usually have a metal disc in place of the rubber top gasket.


YES!!WHAT HE SAID
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#2554353 - 09/25/18 01:30 AM Re: Radiator cap [Re: cdstl]
383man Offline
Too Many Posts

Registered: 01/19/03
Posts: 26879
Loc: Balt. Md
Actually when you think about it the older non-recovery system caps must have had a type of vacuum release. If not when the old system cooled down it would want to collapse the coolant hoses just to start. Ron
_________________________
My car...63 Sport Fury Max Wedge wanna be street car..with new 493 pump gas full exh eng.......10.76 @ 124.49 ! ! ! My page on the cool 62-65 Mopar site ! http://www.1962to1965mopar.ornocar.com/mmo82008.html

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#2554395 - 09/25/18 09:11 AM Re: Radiator cap [Re: 383man]
pushbutton Offline
pro stock

Registered: 11/15/08
Posts: 1424
Loc: tennessee
You don't top the non recovery systems off,if you do it will push coolant out until it reaches a level that allows the coolant to expand when hot. That's the reason you leave the coolant level 1" or more down. If you top it off with the non recovery style cap it will push out coolant to it reaches the level it needs for expansion.

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#2554703 - 09/25/18 05:59 PM Re: Radiator cap [Re: 383man]
RoadRunnerLuva Offline
master

Registered: 01/31/03
Posts: 2897
Loc: Michigan
Originally Posted By 383man
Actually when you think about it the older non-recovery system caps must have had a type of vacuum release. If not when the old system cooled down it would want to collapse the coolant hoses just to start. Ron


I have a 3 row Champion radiator in my Duster. The cap is a 16# stock style "2 PRONG" cap, and what 383Man described above, is what happens to my car when after driving it, and as it cools down...the upper hose collapses and sucks itself inward. When the car is totally cooled off, I take the cap off, the pressure releases, and the upper hose re-expands to normal again. I have an aftermarket Moroso plastic recovery tank installed as well. Should I use a cap from a '96 Ram truck?
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"Get busy living or get busy dying"....

1972 Plymouth Duster...418ci Stroker Small Block
1973 Dodge Charger SE Brougham...400ci Big Block (SOLD)
1971 Plymouth Duster...360 4bbl (SOLD)
1970 Dodge Challenger...340 4bbl (SOLD)
1969 Dodge Dart...440 Big Block (SOLD)
1969 Chrysler 300 Convertible...440 Big Block (SOLD)
1968 Dodge Dart Custom...318 4bbl (SOLD)
1998 Dodge Dakota R/T 5.9 Magnum
2002 Jeep Grand Cherokee 4.0

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#2554715 - 09/25/18 06:51 PM Re: Radiator cap [Re: cdstl]
Supercuda Offline
I Live Here

Registered: 09/04/07
Posts: 13835
Loc: up yours
Champion strikes again
_________________________
They say there are no such thing as a stupid question.
They say there is always the exception that proves the rule.
Don't be the exception.

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#2555361 - 09/26/18 11:59 PM Re: Radiator cap [Re: Supercuda]
RoadRunnerLuva Offline
master

Registered: 01/31/03
Posts: 2897
Loc: Michigan
bump
_________________________
"Get busy living or get busy dying"....

1972 Plymouth Duster...418ci Stroker Small Block
1973 Dodge Charger SE Brougham...400ci Big Block (SOLD)
1971 Plymouth Duster...360 4bbl (SOLD)
1970 Dodge Challenger...340 4bbl (SOLD)
1969 Dodge Dart...440 Big Block (SOLD)
1969 Chrysler 300 Convertible...440 Big Block (SOLD)
1968 Dodge Dart Custom...318 4bbl (SOLD)
1998 Dodge Dakota R/T 5.9 Magnum
2002 Jeep Grand Cherokee 4.0

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#2555529 - 09/27/18 11:44 AM Re: Radiator cap [Re: cdstl]
second 70 Offline


Registered: 02/04/14
Posts: 412
Loc: central il.
I have a three row champion on my hemi and use my windshield washer tank as the recovery tank. When I installed it I also installed a new high flow thermostat that I checked on the stove to see what temperature it opened so I could get an idea on what 180 was on the rallye gauge. So I ran car with cap off to see when opened and checked gauge. Everything was fine until I put cap on at which time it started to get hot. I opened lid on washer tank to add coolant but when I opened the cap it cooled right off. Turns out it was vapor locking the system. Cure I drilled a small hole in top off washer tank no problems in 6 years and no collapsed hoses.
Here’s the cap I use and how the overflow hose goes to bottom of washer tank.


Attachments
F7D6C298-E576-4E7C-AFDD-8A5F06E76884.jpeg

0ECB004A-8C65-4226-B534-95E1E241DE30.jpeg

1D62DC09-E072-4857-A2F7-078D463AFBEC.jpeg




Edited by second 70 (09/27/18 11:47 AM)

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